US3351465A - Photographic diffusion transfer processes utilizing a processing composition containing potassium and lithium ions - Google Patents

Description

United States Patent 3,351,465 PHOTOGRAPHIC DIFFUSION TRANSFER PROC- ESSES UTILIZING A PROCESSING COMPOSI- TION CONTAINING POTASSIUM AND LITHI- UM IONS Dorothy C. Mendelsohn, Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Mass, a corporation of Delaware No Drawing. Filed Dec. 28, 1962, Ser. No. 247,863 7 Claims. (Cl. 96--3) This invention is concerned with photography and, more particularly, with improvements in diffusion transfer processes employing dye developers.

US. Patent No. 2,983,606 issued May 9, 1961, to Howard G. Rogers, discloses and claims processes employing dye developers to form diffusion transfer images. The copending application of Edwin H. Land and Howard G. Rogers, Ser. No. 565,135, filed Feb. 13, 1956, discloses the use of such dye developers in integral multilayer negatives to give multicolor transfer images. The copending application of Milton Green and Howard G. Rogers, Ser. No. 50,851, filed Aug. 22, 1960 (now US. Patent No. 3,173,786 issued Mar. 16, 1965), discloses and claims an improvement in the aforesaid dye developer processes wherein development and transfer are effected in the presence of a quaternary ammonium compound. This invention is concerned with an improvement in dye developer diffusion transfer processes as disclosed in the aforesaid patent and copending applications.

It is a primary object of this invention to provide diffusion transfer processes employing dye developers wherein development and transfer are effected in the presence of potassium hydroxide.

It is a further object of this invention to provide diffusion transfer processes employing dye developers wherein development and transfer are effected in the presence of a substantial concentration of potassium ions, whereby unexpected improvement in such transfer processes are obtained.

Another object of this invention is to provide products and compositions for performing said processes employing potasium hydroxide.

A further object of this invention is to provide diffusion transfer processes, and products and compositions useful in performing said processes, wherein processing is effected in the presence of potassium ions and of quaternary ammonium compounds, preferably .an active methylene quaternary ammonium compound.

Other objects of the invention will in part be obvious and will in part appear hereinafter. I p

The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detail disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of this invention, reference should be had to the following detailed description.

As is now well known in diffusion transfer processes of the type contemplated herein and set forth in detail in the aforementioned issued US. patent and copending U.S. applications, a processing composition is applied to an exposed photosensitive emulsion to effect development thereof, and an imagewise distribution of diffusible, unoxidized dye developers is formed as a function of development. At least a portion of each such imagewise distribution of diffusion dye developer is transferred irnagewise to an image-receiving layer positioned in superposed relationship with said photosensitive emulsion. At the end of the appropriate imbibition period, the image-receiving layer is separated from its superposed relationship with the developed photosensitive emulsion.

The inventive concepts herein set forth provide novel liquid processing compositions for use in such processes.

In carrying out the process of this invention, a photosensitive element containing a silver halide emulsion is exposed and wetted with the novel liquid processing composition of this invention, for example by immersing, coating, spraying, flowing, etc, in the dark, and the photosensitive element superposed, prior to, during or after wetting, on an image-receiving element. In one preferred embodiment, the photosensitive element contains a layer of dye developer, and the liquid processing composition is applied to the photosensitive element in a thin, substantially uniform layer as the photosensitive element is brought into superposed position with an image-receiving element. The liquid processing composition permeates the emulsion to provide a solution of dye developer substantially uniformly distributed therein. As the exposed silver halide emulsion is developed, the oxidation product of the dye developer is immobilized or precipitated in the developed areas, thereby providing an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composition. This immobilization is apparently due, at least in part, to a change in the solubility characteristic of the dye developer upon oxidation, and especially as regards its solubility in alkaline solutions. It may also be due, in part, to a tanning effect on theemulsion by the oxidized developing agent. At least part of each such imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer which layer receives a depthwise diffusion of the transferred, unoxidized dye developer, without appreciably disturbing the imagewise distribution thereof, to provide a reversed or positive, colored image of the image developed in each silver halide emulsion. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. The transfer image is revealed by separating the image-receiving layer from the photosensitive element .at the end of the imbibition period. In an especially useful embodiment, the dye developers are dissolved in a water-immiscible solvent and then dispersed in gelatin to provide the dye developer layers. Numerous examples of suitable dye developers are disclosed in the said US. Patent No. 2,983,606 and copending applications. As set forth therein, a dye developer is a compound which is both a dye and a silver halide developing agent. Particularly useful and preferred dye developers are azo and anthraquinone dyes which contain one or more hydroquinonyl groups.

It now has been found that when an exposed silver halide emulsion is developed in the presence of a dye developer and of a substantial concentration of potassium ions, a number of unexpected and highly beneficial effects result. Imbibition times are substantially reduced and increased film speeds are obtained. A particularly significant improvement occurs when imbibition is effected at relatively low and relatively high temperatures, with transfer images exhibiting superior quality and color separation unexpectedly being obtained over an unusually broad range of temperatures. In general, the advantages of this invention are obtained when at least 50% and more preferably at least to of the alkali metal ions (by weight) present .are potassium ions. When other alkali metal ions also are present, e.g., sodium, lithium, or cesium, particularly useful results are obtained when at least part of such additional alkali metal ions are lithium ions, and the lithium ion concentration preferably is from about 1 to 15%, by weight, of the total alkali metal ions present. In general, it may be said that this invention contemplates the use of potassium hydroxide in a concentration at least equivalent to the normally used sodium hydroxide concentrations, the

pH of the processing composition being of the order of at least pH 12 to 14. Useful results may be obtained with the scope of this invention by the use of potassium hydroxide concentrations within the range of about 2 to 15%, by weight.

The use of potassium hydroxide unexpectedly also has been found to give greater viscosity from a given weight of film-forming material, e.g., hydroxyethyl cellulose, used in the processing composition to facilitate spreading of the processing composition. Where it is desired to use a filmforming material such as carboxymethyl cellulose, the potassium salt preferably is used instead of the sodium salt. The increased viscosity from a given quantity of hydroxyethyl cellulose permits one to reduce the amount of solids in the processing composition. In turn, this has a beneficial effect on the rates of transfer of the dye developers, and helps to increase the resolution of the transfer dye image by reducing lateral diffusion.

In addition to increasing the development rate, the novel potassium hydroxide-containing processing compositions of this invention also provide a significantly shorter development induction period than, for example, a sodium hydroxide processing composition, in processing photosensitive elements of the same construction and composition. The term induction period as used herein is understood to pertain to that period of time from the contacting of the processing liquid with the exposed photosensitive element to the start of development of silver halide. This reduction in induction period is particularly important in obtaining more consistent color quality in transfer images processed over a wide range of temperatures.

In the examples set forth below, reference to a multicolor negative is to a multilayer negative in which the bluesensitive, green-sensitive, and red-sensitive silver iodobromide emulsion layers have positioned behind them, respectively, a yellow dye developer, at magenta dye developer, and a cyan dye developer. A gelatin interlayer is positioned between the yellow dye developer layer and the green-sensitive emulsion, and between the magenta dye developer and the red-sensitive emulsion. Multilayer negatives of this type are disclosed, for example, in FIG. 9 of the previously mentioned US. Patent No. 2,983,606. The dye developer layers are prepared by dissolving each dye developer in a water-immiscible solvent and dispersing the resulting solution in gelatin. The particular dye developers employed, unless otherwise indicated, were:

1,4-bis- [a-methyl-B-hydroquinonyl-et-hylamino] -5,8-

dih drox -a thra u'no e magenta: y y n ql n H3 C H-(IHa 2- [p- 2',5 '-dihydroxyphenethyl) -phenylazo] -4- isopropoxyl-naphthol 1-pheny-1-3-N-n-hexylcarbamyl-4- [p-(2,5-dihydroxyphenethyl) -phenylazo -5-pyrazolone The following examples are given for purposes of illustration and are not intended to be limiting:

Example 1 An image-receiving element was prepared by coating a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine on cellulose acetate-subcoated baryta paper to provide an image-receiving layer approximately 0.40 mil thick. A multilayer, multicolor negative as described above was exposed and a thin layer of processing composition comprising:

Water cc Potassium hydroxide g 11.2 Hydroxethyl cellulose (high viscosity) [commercially available from Hercules Powder Co., Wilmington 99, Del., under the trade name Natrosol 250] g 4.03 Benzotriazole g 3.5 Potassium thiosulfate g 0.5 Lithium nitrate g 0.5 Zinc nitrate g 0.5 N-benzyl-a-picolinium bromide g 2.3

was spread between said image-receiving element and said exposed multicolor negative as they were brought into superposed relationship. After an imbibition period of 1 minute at room temperature, the image-receiving element was separated and contained an excellent multicolor transfer image.

The reduction in imbibition time is illustrated by the following example employing a sodium processing composition:

Example 2 The procedure described in Example 1 was repeated using the following processing composition:

Water cc 100 NaOI-I g 5.17 Hydroxethyl cellulose (high viscosity) [commercially available from Hercules Powder Co., Wilmington 99, Del., under the trade name Natrosol 250] g 4.03 Sodium thiosulfate g 1.15 Benzotriazole g 2.3 N-benzyl-a-picolinium bromide g 2.3

An imbibition period of 1% minutes was required to obtain a multicolor transfer image having comparable density to the image obtained in Example 1. When this experiment was repeated using 8 g. of NaOH and 0.5 g. sodium thiosulfate, the imbibition period was only reduced to 1% minutes. This illustrates the increased transfer rate is a function of the potassium ions, since the higher NaOI-I concentration is substantially equivalent to the KOH concentration used in Example 1.

The potassium processing compositions of this invention are particularly useful with image-receiving elements containing a layer of a nondiifusable acid-reacting reagent, e.g., a polymeric acid, whereby the pH of the image-receiving layer is substantially reduced prior to separation of the image-receiving element from superposed relationship with the negative and subsequent exposure to air. Image-receiving elements of that type are disclosed and claimed in the copending US. application of Edwin H. Land, Ser. No. 234,864, filed Nov. 1, 1962. The following example illustrates the use of such image-receiving elements in this invention.

Example 3 The procedure described in Example 1 was repeated using an image-receiving element containing a layer of a butyl half ester of poly-(ethylene/maleic anhydride), with a layer of polyvinyl alcohol between the above polymeric acid layer and an image-receiving layer of polyvinyl alcohol and poly-4-vinylpyridine, said image-receiving element being prepared as follows: 300 g. of high viscosity poly-(ethylene/maleic anhydride) [commercially available from Monsanto Chemical Company, St. Louis, Mo., under the trade name DX-84031 Resin] was dissolved in 1500 cc. of acetone. 150 g. of n-butyl alcohol and 1 cc. of 85% phosphoric acid were added and the mixture was refluxed for 14 hours. The resulting solution, comprising the partial half-butyl ester of poly-(ethylene/maleic anhydride) was allowed to cool and then coated on a cellulose acetate subcoated-baryta paper to give a layer about 0.8 mil thick. Over this polymeric acid layer was then applied a polyvinyl alcohol layer approximately 0.4 mil thick. An image-receiving layer approximately 0.4 mil thick of a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine then was applied in a manner similar to that used in Example 1 employing a coating solution containing acetic acid. After an imbibition period of 45 seconds, the image-receiving element was separated and contained an excellent, glossy multicolor transfer image. The film speed or Equivalent A.S.A. Exposure Index for this film Was approximately a half-stop faster than obtained with the same negative and image-receiving element using the sodium processing composition of Example 2. The surface of the image-receiving layer had a pH of 11 immediately after separation from the photosensitive element, and this pH was reduced to a pH of approximately 8.5 within 2 minutes, due to the extraction of the alkali ions into the polymeric acid layer.

Example 4 Example 5 The procedure described in Example 3 was repeated using the following processing composition:

Water cc 100 Potassium hydroxide g 11.2 Hydroxyethyl cellulose (high viscosity Natrosol 250) g 3.4 Benzotriazole g 3.5 N-benzyl-a-picolinium bromide g 2.0 Zinc nitrate g 0.5 Potassium thiosulfate g 0.5 Lithium nitrate g 0.5

When such a film assembly was placed in a Polaroid Land camera and conditioned at 95 F., excellent multicolor transfer images were obtained in 30 seconds. Under the same conditions using the 8% sodium hydroxide processing composition of Example 2, the transfer image had a low D even after imbibition periods of 2 minutes. In addition, the transfer image obtained. with the potassium processing composition showed cleaner highlights and less negative fog.

Example 6 The procedure described in Example 5 was repeated, the film assembly and camera being conditioned at 45 F. Very good multicolor transfer images were obtained in a 1% minute imbibition period. Use of an 8% sodium hydroxide processing composition similar to that set forth in Example 2 under the same conditions required 3 /2 minutes imbibition, and resulted in transfer images which were generally less satisfactory. Imbibition periods of approximately 2 /2 minutes using similar processing compositions containing approximately 5% NaOH, 0.5% CsOH and 3% KOH gave transfer images of good density but having a greenish cast. In addition, the latter transfer images frequently exhibit a salting out on the surface thereof, a condition not experienced with the all potassium processing compositions under the same conditions.

Mention already has been made of the beneficial effect upon the dye transfer rates by the use of potassium processing compositions. This should not be considered as merely a speed-up of the individual transfer rates for, in fact, the transfer rates of the individual dye developers also are brought closer together. To study the effect on transfer rates and the formation of multicolor transfer images, a series of integral multilayer negatives were exposed to the same subject and imbibed as in Example 3, at room temperature (75 F.) for 5, 10, 20, 30, 40 and 50 seconds, respectively. It was found that there was very little dye transferred in the 5, 10 and 20 second imbibitions. Dye density began to build up between 20 and 30 seconds, with almost the desired complete dye density being present after 40 seconds imbibition. This test unexpectedly showed that the individual dyes began to build up density on the image-receiving layer at about the same time; in contrast, an analogous imbibition series using sodium hydroxide processing compositions showed a marked difference in the time at which the various dye developers transferred, i.e., there was substantial yellow density before there was much magenta density, and most of the yellow and magenta density was obtained before significant cyan density appeared. This difference in the manner of positive dye build up was completely unexpected. The fact that all three colors begin to appear on the image-receiving layer at about the same time means that the imbibition time becomes less critical, i.e., even though imbibition is terminated before full transfer density is obtained, there is markedly less danger that the transfer image will be seriously deficient in a particular color after a minimum imbibition time has elapsed.

The dye developer transfer images obtained in accord ance with this invention exhibit light stability at least as good as that obtained using sodium processing composition under the same conditions. Where desired, the transfer image may have associated with it an ultraviolet light absorber provided in a layer over the image-receiving layer, as disclosed and claimed in the copending application of Howard G. Rogers, Ser. No. 786,766, filed Jan. 14, 1959 (now abandoned). Alternatively, an ultra-violet absorber may be contained in the processing composition and deposited on the image-receiving layer during imbibition, as disclosed and claimed in the copending application of Howard G. Rogers, Ser. No. 247,866, filed Dec. 28, 1962 (now US. Patent No. 3,249,435 issued May 3, 1966), as a continuation-in-part of said application Ser. No. 786,- 766 (now abandoned). Also, the processing composition may include an arbutin-type glucoside, preferably arbutin per se, as disclosed and claimed in the copending application of Howard G. Rogers, Ser. No. 247,864, filed Dec. 28, 1962 (now U.S. Patent No. 3,287,126).

The copending application of Edwin H. Land and Howard G. Rogers, Ser. No. 565,135, filed Feb. 13, 1956, dis- Example 7 An exposed multilayer negative of the type used in the previous examples was treated with a nonviscous processing composition substantially identical to that in Example 1, the hydroxyethyl cellulose having been omitted. The processing composition was contained in a shallow tray, and the negative was alowed to remain in contact with the processing composition for about 8 seconds. Excess processing solution was then removed from the surface of the negative, which was then passed through a pair of rubber pressure or squeeze rolls in face-to-face contact with an image-receiving element prepared as described in Example 1. After an imbibition period of about 30 seconds, the image-receiving element was separated and contained an excellent multicolor transfer image, characterized by particularly good reds.

Although the preferred image-receiving layer is a mixture of polyvinyl alcohol and poly-4-vinylpyridine (such receiving layers are disclosed and claimed in the copending application of Howard C. Haas, Ser. No. 50,848, filed Aug. 22, 1960, now U.S. Patent No. 3,148,061 issued Sept. 8, 1964), the invention is not limited thereto. Other image-receiving layers are known in the art and may be employed. Similarly, while the preferred embodiment effects development in the presence of a quaternary ammonium compound (as disclosed and claimed in the copending application of Milton Green and Howard G. Rogers, Ser. No. 50,851, filed Aug. 22, 1960, now U.S. Patent No. 3,173,786 issued Mar. 16, 1965), and particularly a quaternary ammonium compound capable of formingan active methylene base in alkali, the invention is not so limited, even though the advantages are most dramatic when such an active methylene quaternary ammonium salt is used.

Processing preferably is effected in the presence of an auxiliary or accelerating silver halide developing agent which is substantially colorless, at least in the unoxidized form. Particularly useful are substituted hydroquinones, such as phenylhydroquinone, 4-methylphenylhydroquinone, toluhydroquinone, tertiary-butylhydroquinone, and 2,5-triptycene diol. These hydroquinones may be employed as components of the processing composition or they may be incorporated in one or more layers of the negative. Particularly useful results are obtained when 4'-methylphenylhydroquinone is dispersed in one or more of the gelatin interlayers and/ or in a gelatin layer coated over the blue-sensitive emulsion layer; the negatives employed in the examples set forth above contained 4'-methylphenylhydroquinone in a layer of gelatin over the bluesensitive emulsion layer.

Where desired, the support for the image-receiving layer may be transparent or opaque. Suitable opacifying agents may be incorporated in the negative and/or positive to permit imbibition to be completed outside of a camera, i.e., in an area exposed to light actinic to the silver halide emulsion.

Suitable hardening agents may be employed in the image-receiving layer coating solution. Particularly useful hardening agents are acrolein condensates, such as that sold by Shell Development Corporation under the trade name Aldocryl Resin X12, and disclosed in the copending application of Lloyd D. Taylor, Ser. No. 229,194, filed Oct. 8, 1962, now abandoned.

This invention is especially useful in composite film units intended for use in a Polaroid Land camera, made by Polaroid Corporation, Cambridge 39, Mass, or a similar camera structure such, for example, as the camera forming the subject matter of U.S. Patent No. 2,435,717,

8 issued to Edwin H. Land on Feb. 10, 1948. In general, such composite film units comprise a photosensitive element, an image-receiving element and a rupturable pod containing an aqueous alkaline processing solution, and may take the form of roll film, sheet film, or film packs. The elements and pod are so associated with each other that, upon processing, the photosensitive element may be superposed on the image-receiving element and the pod may be ruptured tospread the aqueous alkaline processing solution between the superposed elements. The nature and construction of such pods is well known to the art. See, for example, U.S. Patents Nos. 2,543,181 and 2,634,886, issued to Edwin H. Land.

It will be noted that other materials useful in the dilfusion transfer processes may be incorporated into the image-receiving layer or one of the other layers of the image-receiving element. As an exapmle of such a material, mention may be made of development restrainers such as l-phenyl-S-mercaptotetrazole.

As previously noted, the potassium hydroxide preferably is employed in a concentration between about 2 to 15%, by weight. The lower concentrations of KOH are particularly useful in nonviscous processing compositions intended for use in processes like that illustrated in Example 7. The higher concentrations of KOH are particularly useful in embodiments employing image-receiving elements containing polymeric acid layers as illustrated in Example 3.

It is recognized that potassium hydroxide previously has been proposed for use in diffusion transfer processes for obtaining transfer images in silver; see, for example, U.S. Patents Nos. 2,500,421, issued Mar. 14, 1950 and 2,603,565 issued July 15, 1952, both in the name of Edwin H. Land. Such prior disclosures have generally considered potassium hydroxide to be an alkali which might be used as an alternative to sodium hydroxide. The unexpected results obtained herein could not have been predicated on the basis of prior art uses of potassium hydroxide.

It will be noted that the illustrative processing compositions include zinc nitrate and lithium nitrate. Use of salts such as zinc nitrate, zinc acetate, etc., facilitates separation of the processed photosensitive element from the image-receiving element. Use of lithium salts, such as lithium nitrate, lithium acetate, etc., helps to improve film speed and transfer image density, and also improves the overall quality of color transfer images formed at relatively high or relatively low temperatures. Concentrations of lithium nitrate of from about 0.1 to 1% have been found particularly useful. The presence of lithium ions facilitates the use of higher concentrations of antifoggants such as benzotriazole; the use of higher concentrations of benzotriazole give more brilliant and more saturated reds.

Several examples of useful image-receiving elements have been noted above and in the noted patent and copending applications, e.g., polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine. Another particularly useful image-receiving layer is a partial acetal of polyvinyl alcohol with a trialkyl ammonium benzaldehyde quaternary ammonium salt, as dis closed and claimed in the copending application of Howard C. Haas, Ser. No. 71,424, filed Nov. 25, 1960 (now U.S. Patent No. 3,239,337 issued Mar. 8, 1966) The image-receiving element also may contain a development restrainer, e.g., 1-phenyl-5-mercaptotetrazole, as disclosed in the copending application of Howard G. Rogers and Harriet W. Lutes, Ser. No. 50,849, filed Aug. 22, 1960 (now U.S. Patent No. 3,265,498 issued Aug. 9, 1966).

Since certain changes may be made in the above products, compositions and processes without departing from the scope of the invention involved, it is intended that all matter contained in the above description shall be interrupted as illustrative and not in a limiting sense.

What is claimed is:

1. A process of forming multicolor images by diffusion transfer comprising the steps of developing an exposed photosensitive element with an aqueous alkaline processing composition having a pH of at least 12 and containing potassium hydroxide in a concentration of from about 2 to 15%, by Weight, and also containing lithium ions in a concentration of about 1 to 15%, by weight, of the total alkali metal ions present, said photosensitive element con taining a layer of a blue-sensitive silver halide emulsion, a layer of a green-sensitive silver halide emulsion, and a layer of a red-sensitive silver halide emulsion, said silver halide emulsions being superposed on the same support and having associated therewith, respectively, a yellow dye developer, a magenta dye developer, and a cyan dye developer, each of said dye developers containing a hydroquinonyl radical; forming an imagewise distribution of unoXidiZed dye developer in undeveloped areas of each said silver halide emulsion layers as a function of said develop ment, transferring to a superposed image-receiving element, by diffusion, a quantity of each said imagewise distribution of unoxidized dye developer sufficient to form a visible multicolor image thereon, said image-receiving element comprising a support, an image layer thereon including a mordant for a dye, and a layer thereon containing a polymeric acid, reducing the pH of said imagereceiving layer by extraction of alkali ions after said transfer has been effected and thereafter separating said imagereceiving element from said superposed relationship.

2. The process as defined in claim 1, wherein the pH of said image-receiving layer is further reduced, after said separation, by further diffusion of alkali ions to said adjacent layer.

3. The process as defined in claim 1, wherein said 10 image-receiving element includes a layer of an inert polymer which is permeable to said alkali, said layer being positioned between said image, layer and said other layer.

4. The process as defined in claim 1, wherein said composition contains hydroxyethyl cellulose as a thickening agent.

5. The process as defined in claim 1, wherein said potassium hydroxide provides at least to of the alkali metal ions present in said aqueous alkaline processing composition.

6. The process as defined in claim 1, wherein said composition contains 0.1 to 1% lithium nitrate, by weight.

7. The process as defined in claim 1., wherein said composition contains a quaternary ammonium compound capable of forming an active methylene base in alkali.

References Cited UNITED STATES PATENTS 2,584,030 1/1952 Land 96-76 2,661,293 12/1953 Land 96-76 3,087,817 4/1963 Rogers 96-3 2,983,606 5/1961 Rogers 96-29 3,141,772 7/1964 Green 96-29 3,173,786 3/1965 Green et al. 96-29 3,222,168 12/19'65 Land 96-3 3,227,552 1/ 1966 Whitmore 96-3 I. TRAVIS BROWN, Primary Examiner.

NORMAN G. TORCHIN, Examiner.

Claims (1)

1. A PROCESS OF FORMING MULTICOLOR IMAGES BY DIFFUSION TRANSFER COMPRISING THE STREPS OF DEVELOPING AN EXPOSED PHOTOSENTSITIVE ELEMENT WITH AN AQUEOUS ALKALINE PROCESSING COMPOSITION HAVING A PH OF AT LEAST 12 AND CONTAINING POTASSIUM HYDROXIDE IN A CONCENTRATION OF FROM ABOUT 2 TO 15%, BY WEIGHT, AND ALSO CONTAINING LITHIUM IONS IN A CONCENTRATION OF ABOUT 1 TO 15%, BY WEIGHT, OF THE TOTAL ALKALI METAL IONS PRESENT, SAID PHOTOSENSITIVE ELEMENT CONTAINING A LAYER OF A BLUE-SENSITIVE SILVER HALIDE EMULSION, A LAYER OF A GREEN-SENSITIVE SILVER HALIDE EMULSION, AND A LAYER OF A RED-SENSITIVE SILVER HALIDE EMULSION, SAID SILVER HALIDE EMULSIONS BEING SUPERPOSED ON THE SAME SUPPORT AND HAVING ASSOCIATED THEREWITH, RESPECTIVELY, A YELLOW DYE DEVELOPER, A MAGENTA DYE DEVELOPER, AND A CYAN DYE DEVELOPER, EACH OF SAID DYE DEVELOPERS CONTAINING A HYDROQUINONYL RADICAL; FORMING AN IMAGEWISE DISTRIUTION OF UNOXIDIZED DYE DEVELOPER IN UNDEVELOPED AREAS OF EACH SAID SILVER HALIDE EMULSION LAYERS AS A FUNCTION OF SAID DEVELOPMENT, TRANSFERRING TO A SUPERPOSED IMAGE-RECEIVING ELEMENT, BY DIFFUSION, A QUANTITY OF EACH SAID IMAGEWISE DISTRIBUTION OF UNOXIDIZED DYE DEVELOPER SUFFICIENT TO FORM A VISIBLE MULTICOLOR IMAGE THEREON, SAID IMAGE-RECEIVING ELEMENT COMPRISING A SUPPORT, AN IMAGE LAYER THEREON INCLUDING A MORDANT FOR A DYE, AND A LAYER THEREON CONTAINING A POLYMERIC ACID, REDUCING THE PH OF SAID IMAGERECEIVING LAYER BY EXTRACTION OF ALKALI IONS AFTER SAID TRANSFER HAS BEEN EFFECTED AND THEREAFTER SEPARATING SAID IMAGERECEIVING ELEMENT FROM SAID SUPERPOSED RELATIONSHIP.